Apparatus for making metal pellets



Nov. 29, 1960 v. A. RAYBURN APPARATUS FOR MAKING METAL PELLETS Filed Dec.r2, 1959 Q l 9 k INVENTOR Q W V l/A. RA VBUR/V Ar ORA/Ev APPARATUS FORMAKING METAL PELLETS Vincent A. Rayburn, Baltimore, MIL, assignor toWestern Electric Company, Incorporated, New York, N.Y., a corporation orNew York "Filed Dec. 2, 1959, Ser. No. 856,799

Claims. (Cl. 22-1) This invention relates to apparatus for making metalpellets, and more particularly to improved metal pelletizing apparatusof the type utilizing jets of nonoxidizing gases or vapors to break afreely falling stream of molten metal into a plurality of. globules,which solidify to form metal pellets.

Apparatus for making substantially spherical metal pellets of the type.utilizing a rotatable table for shaping and cooling globules of moltenmetal into spherical pellets is: disclosed in V, Rayburn Patent2,739,348; which issued on March 27, 1 956;. This apparatus utilizesjets of nonoxidizing gases or vapors obtained from an external source tobreak up an annular curtain of molten metal. The gases or vapors arepassed through a flutter valve, which intermittently interrupts a steadystream of such gases or vapors to produce a pulsating stream. Thepulsating stream is directed through. nozzles onto the curtain of moltenmetal to break up the curtain of metal into globules of molten metal. Asthe globules of metal move downwardly and outwardly on a curved surfaceof a rotatable cooling table, the globules roll in a declining spiralpath and are thereby shaped and cooled into substantially sphericalpellets.

The patent also discloses that suitable nonoxidizing gases and vapors,supplied from' an external source, are utilized to provide a protectiveatmosphere around the relatively hot globules of molten metal beingshaped and cooled on the rotatable table. Further, the patent. disclosesthat separate electrical motors, energized by an external source, areutilized to operate the flutter valve, to rotate the table and to driveafan in an exhaust system to remove the vapors or gases from theapparatus.

It is desirable to have an apparatus for making substantially sphericalmetal pellets of the type described above, which is simpler inconstruction, more efficient to operate and will produce more uniformspherical metal pellets over a wider range of controllable sizes. It is:also desirable to have pelletizing apparatus which is capable ofoperating as a unit substantially independent of and re mote fromexternal sources of power and external supply sources of gases or vaporsutilized for preventing excessive oxidation of the molten and forbreaking up a stream or curtain of molten metal into globules of moltenmetal.

An object of the present invention is to provide new and improvedapparatus for making metal pellets.

Another object of the invention is to provide an improved metalpelletizing' apparatus of the type utilizing jets of nonoxidizing gasesor vapors to break a freely falling stream of molten metal into aplurality of globules,

.which solidify to form metal pellets.

Still another object of the invention is to provide new and improvedapparatus for making substantially spherical pellets wherein areciprocating piston internal-combustion engine is utilized forproducing a pulsating stream of nonoxidizing gases, a protectiveatmosphere and the mechanical energy necessary for the operation of theapparatus.

An apparatus illustrating certain features of the invention may includea reciprocating piston internal-combustion engine producing an exhaustof pulsating, substantially nonoxidizing gases, and means for directinga flow of the pulsating exhaust gases against a stream of molten metalto break up the stream into a plurality of molten metal globules whichsolidify into pellets.

Other objects and features of the invention will be more readilyunderstood from the following detailed description, when read inconjunction with the accompanying drawings, in which:

Fig. 1 is a fragmentary elevation of apparatus for making metal pelletsembodying certain principles of the present invention, with portionsbroken away for purposes of clarity, and

Fig. 2 is a fragmentary, horizontal section of the apparatus of Fig. 1taken along line 2-2 thereof.

Referring now to the drawings, and more particularly to Fig. 1: thereof,there is shown. an apparatus, designated generally by the numeral 10;for making substantially spherically shaped metal pellets. The apparatusis of the same general construction and operated in a manner similar tothat disclosed in the above-mentioned patent.

The apparatus 19 includes a standpipe, designated generally by thenumeral'ftl, in which. molten metal 12, such as copper, is introduced bya pouring. spout 13. Positioned'. beneath the standpipe 11 is' adomershaped spill head 14', the uppersurface of which matches a concaverecess 16 in the lower portion of the standpipe 11; The molten metal 12flows fromv the standpipe it through a restricted passage 17 of avariable size" formed between the wait of the recess 16" and thedomeshaped top of the spill head 14. The contour of the passage 17 androtary motion of the spill head 14'Wltl1 respect to the concave recess16 cause the molten metal to flow off the domeshapedtop of the spillhead in. the form of a thin-walled, annular curtain l8.

Thethic'kness of the annular curtain 1-8 depends upon the size of thepassage 17 which. may be adjusted by turning the standpipe 11 about itsvertical axis so that a downwardly projecting camrning surface of anannular cam 19, secured fixedly thereto, is rotated with respect to acontiguous upwardly projecting camming surfaceof a stationary annularcam 21. The spill head His secured fixedly to a raised central portion22. of a rotatable, circular, cooling table, designated generally by thenumeral 23, and is rotated by the table with" respect to the standpipe1-1, which remains relatively stationary.

A. plurality of nozzles 24- -2'4 are located adjacent to theposition'where the molten metal curtain 18 falls 01f the edge of thespill head 14 and are spaced circumferential-ly therearound. A stream ofpulsating, nonoxidizing exhaust gases from a reciprocating pistoninternal-combustion engine, preferably from a four-cycle, three cyiindergasoline engine, designated generally by the numeral 26, is supplied toa header 27, on which the nozzles 2424 are mounted, by means of anexhaust pipe 28, connected to an exhaust manifold 29 of the engine 26.The rate of pulsations of the exhaust gases may becontrolled over arelatively wide range by simply changing the speed of the engine 26 byconventional throttling means (not shown).

Pulsating jets of exhaust gasesemerging from the nozzles 24-24 impingeupon and breakup the annular curtain 18 of molten metal 12-fallingdownwardly around the spill head 14. The pulsating jets of exhaust gasesbreak the curtain 18; of the molten metal 12 into a plurality ofglobules or droplets 3131 which fall upon the raised central portion 22of the rotatable table 23.

The table 23 is mounted rotatably on a pair of radial thrust bearings32-32 by a hollow central shaft 33 through which a cooling fluid for thetable, such as water,

is circulated by appropriate means (not shown). A ring gear 34 issecured fixedly around the hollow shaft 33 and is engaged by a worm gear36 keyed to and rotated by a shaft 37. The shaft 37 is connected to apositively, infinitely variable transmission unit 38 driven by means ofa chain and sprocket arrangement, designated generally by the numeral39, from an output shaft 40 of the engine 26. When the curtain 18 of themolten metal is broken into a plurality of molten metal globules 31-31by the pulsating jets of exhaust gases emerging from the nozzles 24-24,the globules fall upon a raised central portion 22 of the table 23 andbegin to roll down the incline toward a substantially horizontal portionof the table, where they solidify into pellets 41-41.

To insure that the pellets 41-41 are of a substantially spherical form,the table 23 should be rotated at such speeds that after the globules31-31 strike the central portion 22 of the table 23 and begin to rollradially downwardly and outwardly they will also roll generallycircumferentially with respect to the table and will then assume arolling motion about an infinite number of axes thereof due to rotationof the table. The globules 31-31 of molten metal then flow downwardlyand outwardly over the surface of the table in the form of constantlyexpanding spirals toward the outer periphery of the table and aredischarged therefrom. The pellets 41-41 thrown from the periphery of thetable 23 strike the inner wall of a hood 42 and fall into cylindricaldrums 43-43 positioned therebelow.

The speed of rotation of the table 23 is preferably maintained at such arate as to prevent undue crowding of the globules 31-31 to eliminate thepossibility of coalescense of the globules while being shaped and cooledto form pellets 41-41, and to prevent the pellets from being thrown offthe table prematurely. The speed of rotation of the table 23 may beadjusted by means of the transmission unit 38 in espective of the speedof the operation of the engine 26.

The temperature of the cooling fluid should also be controlled, since ifthe globules are cooled too quickly they might solidify before attaininga substantially spherical form, and if the globules are cooled tooslowly they might coalesce while still on the table or in the drums, ormight be deformed when they hit the hood 42 while being thrown off thetable 23 or when they fall into the drums 43-43.

The hood 42 is also used to confine gases, fumes and vapors (i.e.exhaust gases emitted by the nozzles 24--24 together with any fumes andvapors arising from the molten metal 12). Since these gases, fumes andvapors will be confined mostly to the upper part of the apparatus 10,the relatively hot globules 31-31 and warm pellets 41-41 on the table23, and being thrown therefrom, would probably oxidize rapidly, ifambient air from outside of the apparatus were permitted to enter thehood 42.

The space under the hood is filled with substantially nonoxidizingexhaust gases from the engine 26 by means of outlets, only one of whichdesignated 44 is shown, arranged circumferentially and projecting froman annular manifold 46. The exhaust manifold 29 of the engine 26 isconnected to the manifold 46 by pipe 47. The exhaust gases of the engine26 emerging from the outlets 44-44 into the space under the hood 42,together with exhaust gas emitted by the nozzles 24-24 and any fumes andvapors arising from the molten metal, exclude air from the spaceunderneath the hood, to such concentration as to render the atmosphereunder the hood substantially nonoxidizing, thereby providing aprotective atmosphere around the relatively hot globules 31-31 and thewarm pellets 41-41.

An exhaust system, designated generally by the numeral 45, is providedto minimize the escape of gases, fumes and vapors from under the hood42. An exhaust fan 48 in the exhaust system 45 is provided to induce thegases from the hood into a suitable discharge stack 49.

Since, when the rate of operation of the engine 26 is varied, the amountof exhaust gas produced thereby and supplied under the hood 42 is alsovaried, it is necessary to vary the suction of the exhaust fan 48accordingly. It is possible to correlate the variations in suction ofthe exhaust fan with the variations in the rate of operation of theengine 26 by operating the exhaust fan 48 from the output shaft 40 ofthe engine 26 by means of a chain and sprocket drive, designatedgenerally by the numeral 50.

By varying the thickness of the curtain of the molten metal, the rate ofpulsations and the pressure of the pulsating jets of the exhaust gasesemerging from the nozzles 24-24, the speed of rotation of the table 23,and the flow of the cooling fluid, it is possible to control the rangeof sizes of the pellets produced by the apparatus 10. Further, byvarying one or all of these factors it is possible to control the sizeand shape of the pellets within each desired size range.

For example, by varying the thickness of the curtain 18 of the moltenmetal, it is possible to increase or decrease the average size of thepellets depending on whether the thickness of the curtain is increasedor decreased, respectively. Similarly, by varying the rate ofpulsations, it is possible to increase or decrease the average size ofthe pellets depending on whether the rate of pulsations is decreased orincreased, respectively. By varying the pressure of the pulsating jetsof the exhaust gases impinging upon the curtain 18 of the molten metal12, the sizes of metal pellets may also be varied within certain limits.

To insure that the pulsations of the gases emitting from the nozzles24-24 are as sharp as practical, the engine 26 should be located so thatthe exhaust gases from the cylinders of the engine will follow theshortest and straightest path to the nozzles, which is practical underthe circumstances. Also, the size of the exhaust pipe 28 should be suchas to permit the transmission of sharp pulsations of the exhaust gaseswithout appreciable dampening. If the cross section of the exhaust pipe28 is too large, the pulsations of the exhaust gases will tend to bedampened out. On the other hand, if the cross section of the exhaustpipe 28 is too small, the pulsations of the exhaust gases will tend tobe dampened or cushioned, due to the resistance of the walls of the pipeto the flow of gases therein. For certain lengths of the exhaust pipe 28the best suitable size of the exhaust pipe to provide for as sharppulsations of the exhaust gas as practical for a given engine may bedetermined experimentally. For example, the cross-sectional area of thepipe 28 may be in a range of from /3 to /s the area of a cylinder headof the engine depending upon the length of the exhaust pipe in rangesfrom to 200 diameters thereof.

The flow of the exhaust gases emerging from the nozzles 24-24 may beregulated by means of a butterfly valve 51 connected in the exhaust pipe28 and a butterfly valve 52 connected in the pipe 47. A chain andsprocket pair, designated generally by the numeral 53, is connected tothe valves 51 and 52 so that both valves can be adjusted by turning asingle handle 54 on the butterfly valve 51. Since all of the exhaustgases of the engine 26 are directed into the hood 42 through the nozzles24-24 and outlets 44, the setting of the butterfly valves 51 and 52 aresuch that when one valve is fully open the other is fully closed.Therefore, when the handle 54 is moved to change the amount of exhaustgases passing through the valve 51, the remaining portion of the exhaustgases produced by engine 26 is directed through the valve 52.

The use of a reciprocating piston engine 26, such as a gasoline ordiesel internal-combustion engine, offers great flexibility, moreeconomical operation and a number of other advantages over the apparatusdisclosed in the above-mentioned patent. The engine 26 produces sharplypronounced pulsations of exhaust gases which are directed to and emittedby the nozzles 24-24,

Ad in thereby eliminating the necessity for maintaining an. external,independent supply of steam, vapors or gases and a separate means forcausing pulsations in the steam, vapors or gases, such as a fluttervalve. The exhaust gases produced by the engine 26 are of asubstantially nonoxidizing nature and consist essentially of carbondioxide, carbon monoxide, water vapor, and traces of unburned gasolineor diesel oil vapors. Traces of unburned gasoline or diesel oil vapors,that inadvertently come into the hood with the exhaust gases, can beburned by combining with traces of oxygen allowed to enter from aroundthe outside of the hood.

In case the engine 26 is cooled by means of a water cooling. system (notshown) the apparatus may be made more substantially self-sufficient byutilizing this cooling system also for cooling the table 23. In such acase, the cooling water for cooling the table 23 and the engine 26 maybe circulated by a singlewater pump (not shown) associated with anddriven by the engine 26.

It will be obvious that various changes and modifications may be madetherein without departing from the spirit and scope of the invention. HWhile theapparatus has been described as being suitable for themanufacture of copper shot or pellets, pellets or shot of other metals,such as iron, lead, zinc, and the like, may be made by means ofapparatus of this same general design.

What is claimed is:

1. Apparatus for making metal pellets from a freely falling stream ofmolten metal, which comprises a reciprocating piston internal-combustionengine producing an exhaust of pulsating substantially nonoxidizinggases, and means for directing a flow of said pulsating gases against afreely falling stream of molten metal to break the stream into aplurality of globules of the molten metal, which solidify to form metalpellets.

2. Apparatus for making metal pellets from a freely falling stream ofmolten metal, which comp-rises a reciprocating pistoninternal-combustion engine producing an exhaust of pulsatingsubstantially nonoxidizing gases, and means for converting saidpulsating gases into a plurality of relatively high velocity pulsatingjets and for directing said pulsating jets against the freely fallingstream of molten metal to break the stream into a plurality of globulesof the molten metal, which solidify to form metal pellets.

3. Apparatus for making metal pellets from a freely falling stream ofmolten metal, which comprises a reciprocating piston internal-combustionengine producing an exhaust of pulsating substantially nonoxidizinggases, means for converting said pulsating gases into a plurality ofrelatively high velocity pulsating jets and for directing said pulsatingjets against the freely falling stream of molten metal to break thestream into a plurality of globules of the molten metal, which solidifyto form metal pellets, and means for varying the volumetric rate of flowof the molten metal in the stream to vary the average size of thepellets produced by said apparatus.

4. In apparatus for making metal pellets including means for producing acurtain of a freely falling stream of molten metal, a plurality ofnozzles for directing gases at relatively high velocities against saidcurtain of molten metal, and a rotatable table toward which the streamof molten metal is falling, the improvement which comprises areciprocating piston internalcombustion engine connected operatively tosaid table for rotation thereof, said engine producing an exhaust ofsubstantially nonoxidizing pulsating gases, and means for conducting atleast a portion of said exhaust gases to said nozzles whereby relativelyhigh velocity jets of pulsating gases impinge upon the stream of moltenmetal and break the stream into a plurality of molten metal globules.

5. In apparatus for making metal pellets including means for producing afreely falling curtain of molten metal, a plurality of nozzles fordirecting gases at relatively high velocities against the freely fallingcurtain of molten metal, and a rotatable table toward which the curtainof molten metal is falling, the improvement which comprises areciprocating piston internalcombustion engine connected operatively tosaid table for rotation thereof, said engine having an exhaust ofsubstantially nonoxidizing pulsating gases, first means for conducting afirst portion of the exhaust gases to said nozzles whereby relativelyhigh velocity jets of pulsating gases impinge upon said curtain ofmolten metal and break the curtain into a plurality of molten metalglobules, and second means for conducting a second portion of theexhaust gases into surrounding relationship with the table to form aprotective nonoxidizing atmosphere thereabout.

6. In apparatus for making metal pellets including means for producing afreely falling curtain of molten metal, a. plurality of nozzles fordirecting gases at relatively high velocities against the freely fallingcurtain of molten metal, and a rotatable table toward which the curtainof molten metal isfalling, the improvement which comprises areciprocating piston internal-combustion engine connected operatively tosaid table for rotation thereof, said engine having an exhaust ofsubstantially nonoxidizing pulsating gases, first means for conducting afirst portion of the exhaust gases to said nozzles whereby relativelyhigh velocity jets of pulsating gases impinge upon the curtain of moltenmetal and break the curtain into a plurality of molten metal globules,second means for conducting a second portion of the exhaust gases intosurrounding relationship with the table to form a protectivenonoxidizing atmosphere thereabout, and valve means for controlling theflow of the exhaust gases through said first and said second conductingmeans in any desired ratio of portions of the total exhaust gases of theengine.

7. In appaartus for making metal pellets including means for producing afreely falling curtain of molten metal, a plurality of nozzles fordirecting gases at relatively high ve ocities against said curtain ofmolten metal, and a rotatable table toward which the curtain of moltenmetal is falling, the improvement which comprises a reciprocating pistoninternal-combustion engine connected operatively to said table forrotation thereof, said engine producing an exhaust of substantiallynonoxidizing pulsating gases, means for conducting at least a portion ofsaid exhaust gases to said nozzles whereby relatively high velocity jetsof pulsating gases impinge upon the curtain of molten metal and breakthe curtain into a plurality of molten metal globules, and means foradjusting the rotational speed of the table independently of the speedof the engine.

8. In apparatus for making metal pellets including means for producing afreely falling curtain of molten metal, a plurality of nozzles fordirecting gases at relatively high velocities against said curtain ofmolten metal, and a rotatable table toward which the curtain of moltenmetal is falling, the improvement which comprises a reciprocating pistoninternal-combustion engine connected operatively to said table forrotation thereof, said engine producing an exhaust of substantiallynonoxidizing pulsating gases, and means for conducting at least aportion of said exhaust gases to said nozzles whereby relatively highvelocity jets of pulsating gases impinge upon said curtain of moltenmetal and break the curtain into a plurality of molten metal globules,said engine also having means for adjusting the speed thereof to controlthe rate of pulsation of the gases in the jets.

9. In apparatus for making metal pellets including means for producing afreely falling curtain of molten metal, a plurality of nozzles fordirecting gases at relatively high velocities against the freely fallingcurtain of molten metal, a rotatable table toward which the curtain ofmolten metal falling, the improvement which com- "games prises areciprocating piston internal-combustion engine connected operatively tosaid table for rotation thereof, said engine having an exhaust ofsubstantially nonoxidizing pulsating gases, first means for conducting afirst portion of the exhaust gases to said nozzles whereby relativelyhigh velocity jets of pulsating gases impinge upon said curtain ofmolten metal and break the curtain into a plurality of molten metalglobules, second means for conducting a second portion of the exhaustgases into surrounding relationship with the table to form a protectivenonoxidizing atmosphere thereabout, and means for exhausting saidexhaust gases from the apparatus for preventing contamination of spaceimmediately surrounding said apparatus with said exhaust gases, saidexhaust means including a rotatable impeller connected operatively tosaid engine for rotation thereby.

thereof, said engine having an exhaust of substantially nonoxidizingpulsating gases, first means for conducting a first portion of theexhaust gases to said nozzles whereby relatively high velocity jets ofpulsating gases impinge upon the curtain of molten metal and break thecurtain into a plurality of molten metal globules, second means forconducting a second portion of the exhaust gases into surroundingrelationship with the table to form a protective nonoxidizing atmospherethereabout, valve means for controlling the flow of the exhaust gasesthrough said first and second conducting means in any desired ratio ofportions of the total exhaust gases of the engine, and means foradjusting the rotational speed of the table independently of the speedof the engine, said engine also having means for adjusting the speedthereof to control the rate of pulsation of the gases in the jets.

References Cited in the file of this patent UNITED STATES PATENTSRayburn Mar. 27, 1956

